William warwick stenning



Patented Oct. 21, 1924.

UNITED STATES PATENT OFFICE.

WILLIAM WARWICK'S'I'ENNING, PERCY THOMAS WILLIAMS, WALTER HENRY BEAS- LEY, AND ARTHUR BERESFORD MIDDLETON, 01? LONDON, ENGLAND, ASSIGNORS TO MINERALS gEPARATION NORTH AMERICAN CORPORATION, OF NEW YORK,

N. Y., A CORPORATION.

TREATMENT OF SMALL OR FINELY-DIVIDED COAL.

No Drawing.

utilizable, as in briquetting, and particularly to a process of treatment of coal by coating with a'flocculating mediumthe particles of coal suspended in a circuitliquor, whereupon the circuitliquor can readily be removed by the application of pressure. Such a process is described in United States 0 patent application Serial No. 404,106 filed 17th August 1920.

In such a process, when using a flocculating medium such as molten pitch, which is an effective binding agent, the coated coal particles can eventually be pressed into strong briquettes, but when briquettes of this character are not required, other flocculating agents may be employed. In this case also, to facilitate handling, the treated coal may be pressed into blocks which, although relatively soft, are sufficiently coherent and are herein referred toas briquettes.

The objects of the present invention are to reduce the quantity of flocculating agent required, and to economize the amount of heat which may be needed in the preparation for briquetting The term circuit liquor is employed herein to include water or any other aqueous liquor in which the coal particles may be suspended during the treatment.

Cal

According to the present invention the. coal particles are treated by agitation in a. circuit liquor together with finer coal par- Application filed November 11, 1922. Serial No. 600,407.

and flocculated, can be made to play the part of a binding medium for coarser particles. The fine particles become attached to the coarse particles, the binding medium on thesurface of the fine particles serving effectively to unite the whole together in the subsequent operation of briquetting.

We have found by experiment that the amount of binding medium required in such a treatment is considerably less than the amount required when the binding medium is added to the aggregate of fine and coarse coal.

The invention includes a process for the treatment of finelydivided coal wherein fine coal particles are fiocculated by agitation in aqueous suspension with a flocculating medium and are subsequently mixed with coarser coal particles so as to fiocculate the mixture and render the coal readily separable from associated water.

The invention further includes a process for the treatment of finely-divided coal wherein the coal is separated into fractions containing respectively coarser and finer particles, the finer particles are treated with a fiocculating medium and'the coarser particles are thereupon suspended in circuit liquor and treated by agitation with the flocculated finer particles, with or without the further addition of a binding medium.

Preferably the finer particles are coated with the flocculating medium by agitating 1 them, while in aqueous suspension, with the addition of the fiocculating medium.

\Ve have found that the heat consumed during the briquetting process can be economized, because the coal originally suspended in cold circuit liquor, can be floccu- I lated by treatment in the cold so as to be separated from that liquor or at least from a substantial part thereof, and if heat is necessary for the subsequent operations the introduction of cold circuit liquor along with the fine coal can be obviated or minimized.

The invention therefore includes a process for the treatment of finely-divided coal as set forth above, wherein. the initial treatment of the finer coal particles with the flocculating medium is carrieu out in a cold circuit liquor by the use of an agent capable of producing flocculation in the cold, such as anthracene oil, tar or the like. Pret'en ably, the fine coal al'ter flocculation is separated from cold circuit liquor by mechanical means (for example filtration) and is thereafter treated with coarser coal in hot circuit liquor, fiocculat'ed and separated from the liquor which is reused :tor the treatment of further quantities of mixed fine and coarse particles.

Thus, according to one form of the present invention, the coal suspended in water oraqueous circuit liquoris treated by screening,

lassification, or the like known method to separate the fine coal "suspended in the water or circuit liquor from the coarse coal, the fine coal is nominated in the cold circuit liquor by the'addition of a suitable oil, tar or mixture of tar and pitch or the like while the pulp is being subjected to agitation and/or aeration, the said fine coal is separated from cold circuit liquor by filtration or the like mechanical method, and the fine coal together with the coarse coal with or without a binder such as molten pitch or finely ground solid pitch are added to and mixed by agitation with a hot circuit liquor, and finally the hot circuit liquor is moved from the coal by filtration or pressure and again used, while the hot coal is converted into briquettes substantially free from water by pressure in a mould oi suitable design. 7 r

The size of the coal particles and the selection of the proper ratio of fine and coarse particles will vary according to, circumstances and in carrying out the present invention, the extent to which classification is carried may be varied so as to obtain the best economical results. We have found with the coals we have tried that when the coal to be treated will ass a screen of 10 meshes to the linear inch, 1; e fines that will pass through a screen of 60 80 meshes to the linear inch should be separated; in such cases the fines removed usually amount to about 9 by weight of the total coal.

Apparently the fine particles should be present in suflicient quantity to cover or coat the surfaces of the coarser particles more 01: less closely, and the quantity of hinder or fiocculating agent required seems to be a t'u'nction of the total surface of the finer particles which are to be coated with it. The total collective surface or? the particles in a sample of finely divided coal can be estimated by sitting it into various grades and estimating the surface of each grade separately on the assumption that all the particles in a grade are of an average size and have asunple cubical or other probable shape.

Takingfor example dull coal from Powell Dufi'ryn Colliery in South Wales, crushed to Surface screen. exlmsei Weight.

agitatioi'i with aeration, the binder being added 111 liquefied form, requires 7% or binder to produce effective flocculation of the particles which will lead to the production of a first class briquette when subjected to proper pressure in a suitable mould.

Treating the coal, however, according to the present invention, the fines of a size smaller than mesh are separated by treating the concentrates in the form of a mobile pulp on a screen or sieve of 60 meshes to the linear inch.

The finer particles which pass through the I screen with the water amount by weight to about one-quarter of the coal concentrates. The coarser particles are by this step separated trom the bulk of the water. The sepa rated fines, suspended in water, are agitated vith an amount binder equal to 5% on the total weight of the coal. Treatment is arried out in a heated circuit liquor and the binder is added in a liquefied condition. litter flocculation of the fines in this way the coarser particles, larger than 60 mesh and comprising 75.9 by weight of the coal are admixed with the coated and fiocculated finer particles. l llocculati-on results off the whole mass, and on subjecting this to pressure in a briquetting pressa briquette results 01 equal quality with that which required 7% ol binder when the whole of the coal was treated together in one step. i

It seems evident that in this particular case 5% of binder is sufiicient to cover effectively 3022 square inches or" surface exposed on the portion of the coal smaller than 60mesh, but is insufiicient to cover effectively 3851 square inches exposed on the total product. Furthermore, apparently the quantity of binder required is approximately proportional to the exposed surface which it is required to coat directly. At the same time the amount of fines initially treated cannot be indefinitely reduced, as a sulficient quantity must be used to coat the coarser particles and act as an efficient binder or matrix therefor. The surface of the fines should in practice apparently be at least three times greater than the surface of the coarser particles for the best results.

Many reagents, other than the mixture of pitch and tar referred to above, may be used to flocculate'the fine coal, and in some cases after flocculation of the fines an additional agent may be added when treating fines and coarse together. This is particularly the case where the agent used for the fines is one which will not lead to the production of briquettes of the desired strength. In practice, for briquetting purposes, it is always necessary to select an agent which helps, or at least does not hinder the final briquetting operation. Such agents are the coal-tar product. known as anthracene oil, or an oil containing a substantial proportion of naphthalene or phenanthrene; the amount of such oil that it is permissible to use is limited by the condition that the use of too much oil produces weak briquettes; we have found I; that a quantity of anthraeene oil amounting till to 1% of the total weight of coal will serve to floeculate the fines, and an excellent briquette can be formed by adding the separated fine and coarse coal together with molten pitch, finely divided hard pitch or similar binder amounting to 4% of the total weight of coal, and mixing the whole in a circuit liquor at 80 to 100 C.

The following alternative procedure, us-

ing the same coals above described, illustrates the use of anthracene oil. As before, the coal is ground to pass a 10 mesh screen and subjected to concentration by the frothflotation process for the removal of ash. The concentrate is still mixed with water, and in the form of a mobile pulp it is treated on a screen or sieve of or 80 meshes to the linear inch. The fines are thereby sepa rated, with the bulk of the water, in amount as before of about one-quarter by weight of the coal concentrates.

The aqueous suspension of finer particles (which is not heated) is introducedinto an agitation apparatus, preferably an apparatus of the general type employed for agitating the pulp in the frothflotation process, i. e., an apparatus which affords both agitation. and aeration. During the agitation there is added to the pulp a small proportion, say 1%, of anthracene oil, this percentage being measured on the total weight of coal. By this process the finer particles become coated with the oil and flocculated, and can therefore be removed from the cold liquor by settlement. and decantation, or by screening, or byfiltration.

Thefinal preparation of all the coal is eflfected in a hot circuit liquor which is used repeatedly. The coarser particles, substantially free from water, are added to the hot circuit liquor at 80 C. and the fiocculated finer particles are also added, together with 4% of molten pitch or finely divided solid pitch measured on the total weight of coal. Themixture is effected during agitation, preferably with aeration.

When the coated finer particles have had adequate opportunity of becoming attached to th coarse particles, the solid matter as a whole is separated from the hot circuit liquor, again by settlement and decantation, or screening, or filtration, and the solid matter is directly subjected to briquetting, say in a briquetting press.-

Thefollowing example gives the results in detail obtained upon coal from the Saar Valley in France. The coal consisted of a mixture of bright and dull coaltogether with carbonaceous shale. The ash content was 24.97% but this was reduced by flotation concentration to 9.12%.

This concentrate was screened to separate fines of a size such as to pass an aperture of 0.008 inch in linear dimensions and the finer portion was treated in an acid circuit liquor containing 1 lb. sulphuric acid per ton of coal. The treatment was carried out in a cell provided with an agitator of the type used in the frotl1fiotation process, i. e., a cell provided with an agitator which gives vigorous agitation and aeration. A binding medium was added containing three parts of pitch and two parts of tarin the proportion of 5% of binding medium on the total weight of the coal (fine and coarse). Steam was then admitted and the temperature of the pulp was raised to 90 C. After the flocculation of the finer portion of the coal in this way, the coarse particles were added during agitation, and the whole material was thus flocculated. Thereafter it was drained and briquetted under pressure of 2 tons per square inch. The briquettes were eventually coked for two hours at a temperature gradually rising to 1040 C. and yielded a coke having a crushing strength of 2430 lbs. per square inch.

It will be noted that in this test the whole of the binding medium was employed in the initial operation on the fines, and the treatment of the tines was therefore concluded in a hot circuit, owing to the large proportion of pitch in the binder. It has, however, already been pointed out that the use of a hot circuit for the fines is not essential.

In place of the mixture of tar and pitch a mixture of 11/; parts of naphthalene to 3 parts of pitch can be employed, the quantity amounting as before, to 5% of the total weight of the coal.

What we claim as our invention, and desire to secure by Letters Patent is 1. A process for the treatment oil finely divided coal wherein the coal particles are treated by agitation in a circuit liquor to gether with finer coal particles which have previously been coated with a fiocculating medium.

2. A process for the treatii'ient of finelydivided coal wherein the coal particles are treated by agitation with aeration in a circuit liquor together vith finer coal particles which have previously been coated with a fiocculating medium.

3. A process for the treatment oi finelydivided coal wherein fine coal particles are fiocculated by agitation in aqueous suspension with a fiocculating medium and are subsequently agitated in aqueous suspension with coarser coal particles so as to fiocculate the mixture and render the coal readily separable lrom associated water.

4. A. process for the treatment oi finelydivided coal wherein the coal is separated into fractions containing respectively coarser and finer particles, the finer particles are treated with a fiocculating medium and the coarser particles are thereupon suspended in circuit liquor and agitated so as to be flocciilated with the treated finer particles.

5. A process for the treatment of finelydivided coal wherein fine coal particles are flo'cculated by agitation in aqueous suspension with a fiocculating medium and are subsequently agitated in aqueous suspension with coarser coal particles so as to flocculate the mixture and render the coal readily separable from associated water with the further addition of a liquefied binding medium.

6. A process for the treatment of finely divided coal wherein the coal is separated into fractions containing respectively coarser and finer particles, the finer particles are coated with a fiocculating medium by agitating them, while in aqueous suspension, with the addition of the fio'cculating medium, and the coarser particles are thereupon suspended in circuit liquor and agita-ted so as to be 'fiocculated with the coated finer particles.

7. A process for the treatment of finely divided coal wherein fine coal particles are fiocculated by agitation in aqueous suspension at normal atmospheric temperature with an agent capable of producing flocculation at that temperature and are subsequently agitated in aqueous suspension with coarser coal particles so as to fioccu-late the mixture and render the coal readily separable from associated water.

divided coal wherein fine coal particles are fiocculated by agitation in aqueous suspension at normal atmospheric temperature with an oily coal tar product and are sub-- sequently agitated in aqueous suspension with coarser coal particles so as to fi-occulate the mixture and render the coal readily separable from associated Water. 7

9. A process for the treatment of finely divided coal wherein fine coal particles are flocculated by agitation in aqueous suspension at normal atmospheric temperature with authracene oil and are subsequently agitated in aqueous suspension with coarser coal particles so as to flocculate the mixture and render the coal readily separable from associated water.

10. A process tor the treatment of finely divided coal wherein fine coal particles are fioccul-ated by agitation in aqueous suspension at normal atmospheric temperature with an agent cap-able of producing flocculation at that temperature, are separated from cold circuit liquor, and are thereupon agitated with coarser coal particles in a heated circuit liquor with the addition of a liquefied binding medium so as to flocculate the mixture and render it readily separable from associated water.

11. A process for the treatment of finely divided coal wherein fine coal particles are fiocculated by agitation in aqueous suspension at normal atmospheric temperature with an agent capable of producing flocculation at that temperature, are separated from cold circuit liquor, are there-upon agitated with coarser coal particles in a heated circuit liquor with the addition of a liquefied binding medium so as to fl-occ-ulate the mixture and render it readily separable from associated water,an-d are subjected to pressure to expel water and produce briquettes.

12. A process for the treatment of finely divided coal wherein fine coal particles are fiocculated by agitation in aqueous suspension by the addition oi a suitable reagent, are thereupon agitated with coarser coal particles in aqueous suspension so as to fioccul-ate the mixture and render it readily separable from water and are subjected to pressure to expel water and produce briquettes. r

13. A process for the treatment of finely divided coal wherein coal particles are treated by agitation in a circuit liquor together with finer coal particles which have previously been coated with a flocculating medium and are subjected to pressure to expel water and produce briquettes,

14. A process for the treatment of finely divided coal wherein fine coal particles are fiocculat-ed by agitation in aqueous suspension at normal atmospheric temperature 8. A process for the treatment of finely with anthracene oil, are separated from cold circuit liquor, are thereupon agitated with coarser coal particles in a heated circuit liqnor with the addition of a liquefied binding medium so as to fiocculate the mixture and render it readily separable from associated Water, and are subjected to pressure so as to expel water and produce briquettes.

15. A process for the treatment of finely divided coal wherein coal particles are treated by agitation in a circuit liquor together with a sufficient quantity of finer coal par ticles which have previously been coated with a flocculating medium to substantially coat the coarser particles with finer ones distributed over their surface, and to render the whole of the coal readily separable from water.

16. A process for the treatment of finely divided coal wherein relatively coarse coal particles are treated by agitation in a circuit liquor together with finer coal particles in sufiicient quantity to have a total surface at least three times greater than that of the coarse particles, the finer particles having previously been coated on their surfaces with a fiocculating medium, so as to render the whole of the coal readily separable from water.

17. A briquette consisting of coarser and finer grades of coal particles, the finer particles being coated on their surfaces with a fiocculating and binding medium and being distributed over the surfaces of the coarser particles in suflicient quantity to act as a binder in uniting them together.

18, A fuel product consisting of coarser and finer grades of coal particles, the finer particles being coated on their surfaces with a fiocculating and binding medium and be ing distributed over the surfaces of the coarser particles in sufficient quantity to render the Whole mass readily separable from water.

19. A fuel product consisting of coarser and finer coal particles in such ratio that the total surface of the finer coal particles is more than three times the total surface of the coarser particles, the finer particles being coated on their surfaces with a flocculating and binding medium and distributed over the surfaces of the coarser particles so as to render the whole mass readily separable from water.

20. A briquette consisting of coarser and finer coal particles in such ratio that the total surface of the finer coal particles is more than three times the total surface of the coarser particles, the finer particles being coated on their surfaces with a flocculating and binding medium and distributed over the surfaces of the coarser particles so as to act as a binder in uniting them together.

In testimony whereof we have signed our names to this specification in the presence of two subscribing Witnesses.

Percy 

